The biotechnology industry uses different manufacturing systems for creating aseptic and sterile connections between process containers and equipment, such as plastic bags and pumps. A known manufacturing system uses controlled environments such as clean rooms or cabinets to ensure aseptic connections during manufacture. When necessary connections are made in such a controlled environment that breaches sterile tubing and piping, the environment does not contaminate the fluid flow passage. However, maintaining a clean room is time consuming, difficult and costly to validate
For example separation or reaction systems such as chromatography systems, filter systems or bioreactor systems have today at least partly been provided as disposable systems. This eliminates the need for cleaning and cleaning validation before processing, in between processes and cycles or after processing before re-use as required for conventional re-usable equipment. With disposable systems cross-contamination is avoided.
Bioburden control of single-use equipment during manufacturing of the equipment itself is required to eliminate cleaning needs before bringing single-use equipment into product contact. This is usually achieved by manufacturing of single-use equipment in controlled environment (clean room), often followed by sterilisation processes (gamma irradiation). The demands of the level of bioburden control can differ for different applications. However, bioburden control to a certain degree of the equipment is not only required for some applications, but also considered as the preferable for most of the applications using disposable equipment. The production of this equipment in controlled environments is required to guarantee a low initial level of contaminants prior to the bioburden control procedure. Sterility and asepsis are terms used to define the state of a system, a piece of equipment or a fluid conduit as being in control of bioburden levels to different degrees.
Many manufacturing systems use disposable plastic bags connected to flexible thermoplastic tubes, which requires special connections to assure that the bags and tubes remain clean and sterile. Known are also pre-sterile bags and tube sets which can be supplied with the appropriate special disposable aseptic connection system fittings already in place. These connections are simple, repeatable and validatable but they normally have to be applied during manufacture of the sets and are not amenable to the setting up of tailor-made systems directly in the bioprocess facility.
Sterile welding of flexible thermoplastic tubing, where lengths of tubing are cut and welded together under aseptic conditions is an attractive alternative which provides a higher degree of flexibility. Equipment for such welding is commercially available and different constructions have been described in e.g. U.S. Pat. No. 4,516,971, EP723851A2, WO2013096038A1, U.S. Pat. Nos. 7,398,813 and 6,705,372. Sterile welding is particularly common in medical settings, e.g. assembly of sterile circuits for hemodialysis. It is also quite commonly used in bioprocess settings, although a drawback of the available technology is that several separate welders have to be used for tubing of different diameters which are often used simultaneously in different parts of a single bioprocess to accommodate ranges of flow-rates, pressures etc.
Accordingly there is a need for a welding apparatus which enables welding of tubing over a range of different diameters.